Ooh... ahh,
I lost my bra,
I left my knickers in my boyfriend's car.
This weighty verse differs from the infantile whimsy of ta-ra-ra-bum-di-ay, in that it contains a powerful moral element.
In ta-ra-ra-bum-di-ay, the loss of the knickers was spontaneous, and not the result of moral turpitude. As a result, the knickers were returned by the gracious Fates.
Here, however, the knickers are lost as the direct result of pre-marital sex. Notice that the loss of a bra - a powerful symbol of female sexuality - compounds the devastation. Neither garment is (at least, explicitly) returned, leaving us to assume that they were either found by a slack-jawed vicar, who - mistaking their function - used them as hanging baskets in his garden.
Also note that only the woman is punished. That is because women are temptresses, and all sex and betrayal in the world is a result of their vile chicanery and desire for ever-more children, as documented in Ace of Bass's hit single "All That She Wants Is Another Baby".